1. Field of the Invention
The present invention generally relates to an image processing apparatus which displays pictures or movies on a computer screen while recording a digital signal or outputting a video signal when the video signal is inputted. More particularly, the present invention relates to an image processing apparatus which prevents copying when a video signal including a copy guard signal is inputted.
2. Description of the Related Art
Since an information device such as a high performance personal computer or a large capacity storage device, or a high quality digital VTR (Video Tape Recorder) has come into existence recently, it has become easy to copy or duplicate pictures or audio programs using a computer technology. Therefore, the technology both to protect copyright and to give users their convenience has become important increasingly.
Regarding a digital picture or a digital audio provided through an internet or a television, it is well known that the following, for example, is proposed. The sender of programs admits to record programs or music on videotape or tape, step by step, such as; (1) without any restriction, (2) only once, or (3) prohibits from recording completely, and those are distinguished at the receiver.
FIG. 1 shows a drawing for explaining an example of recording or outputting to duplicate a digital signal. The digital picture provided through a line 180 using the internet has been downloaded to a hard disk apparatus 181, and reproduced on a computer screen 182 by an information device such as a personal computer.
If the information device has a function for outputting video signals, it is possible to connect to a television and to reproduce the same picture on the television screen 183 as the computer screen 182.
Regarding an analogue signal, for example, in a VTR currently in use, there are software, or programs provided with some kind of copy guard process in order to protect against illegal copying. And it is possible to display the program normally on the television but the image quality, even if it was recorded, becomes worse at VTR for household use, then it is impossible to record the program on videotape substantially.
In case of a video printer that prints color images out of videotape, it is known that the printer has a function for protecting output of the printer against illegal copying. According to Japanese laid open patent applications H4-294697, or Japanese laid open patent applications H9-83920, for example, some printer controls AGC (Auto Gain Control) circuit for the period of time and other printer prohibits to issue the picture signals, when a copy guard signal is detected on the videotape.
FIG. 2 shows a drawing for explaining an example of recording and duplicating of a video signal. The analogue picture provided on the videotape 190 currently in use can be reproduced normally on a television screen 183 using VTR (playback) 191 (FIG. 2 (a)), even if a copy guard is applied to the videotape.
However, in case of recording the videotape 190 to the videotape 193, using VTR (playback) 191 and VTR (recording) 192 (FIG. 2 (b)), if a copy guard is applied to the videotape 190, recording itself may be impossible. The picture becomes very dark, or the image quality becomes worse when it is reproduced, even if it could be recorded. Hence, it is possible to protect against illegal copying as a result.
FIG. 3 and FIG. 4 are time charts for explaining an example of a copy guard signal. There is a video signal not including the copy guard signal in FIG. 3. A video signal of a television screen is generally composed of vertical synchronizing pulses 200 leading other pulses at each screen, horizontal synchronizing pulses 201, and image signals 202 at each line. The copy guard signal is inserted between a vertical blanking interval, not displayed at the television screen.
A video signal including the copy guard signal 210 is shown in FIG. 4. The copy guard signal 210 has a higher level than the image signal 202 in voltage. Therefore, the AGC circuit of a recording and reproducing device recognizes the high voltage level of the copy guard signal 210 as an ordinary level and makes the voltage level of image signal 202 lowered relatively when the video signal is inputted. Hence, the picture recorded becomes very dark, and it is possible to protect against illegal copying.
Pictures of a videotape current in use are also displayed at a screen of either a personal computer or a workstation. FIG. 5 and FIG. 6 are drawings for explaining examples of a video signal and a computer screen.
Both an input terminal for a video signal and an output terminal for a video signal are provided at a computer. VTR 191, for example, is connected to the input terminal 220 for a video signal which comes from a videotape 190, and a television 183 is connected to the output terminal 221 for a video signal.
FIG. 5, a video signal and a computer screen (1), shows what pictures of the videotape 190 are inputted and monitored at the computer screen 182, and outputted and displayed at the whole screen of the television 183. FIG. 6, a video signal and a computer screen (2), shows what pictures of the videotape 190 are inputted and combined with other windows at the computer screen 182, and outputted and displayed at the television screen 183.
In each case, if a substitute for the television 183, for example, VTR (recording) is connected to a computer, it will be possible to record the pictures of videotape 190 using the computer.
In addition, since a storage apparatus, for example, a hard disk device 181 is connected to the computer, it becomes possible to record the digitized pictures which are inputted into the computer.
The picture stored at the storage apparatus such as the hard disk device 181 or CD-ROM device is reproduced at the computer screen, therefore, if the computer has the output terminal 221 for a video signal, it will be possible to record the picture on a videotape using VTR (recording). If a storage apparatus with a high speed memory and sufficiently large enough comes into existence, even if the picture quality of the videotape becomes higher, it will be possible to store the picture keeping the high quality and to output the video signal reproducing the high quality picture. FIG. 7 shows a block diagram for explaining an example of the prior art. A video decoder 3 digitizes a video signal 240 inputted at an input terminal 220 for a video signal. Digitized video information is stored as a screen information at a video memory 5. When the video information is inputted, the input data from the video decoder 3 is stored into the video memory 5 by a graphics controller 6. When a video information is outputted from a hard disk device 181, the output data is stored into the video memory 5 as every screen information by the graphics controller 6. RGB signal is outputted to a display device 9 out of the graphics controller 6, and a digital signal is outputted to a video encoder 7 out of the graphics controller 6. A video signal 241 converted to analogue from digital, at the graphics controller 6, is outputted to an output terminal 221 for a video signal.
CPU (Central Processing Unit) 4 controls both recording and reproducing the picture information digitized. The hard disk device 181 stores the picture information digitized under the control of CPU 4. In case of reproducing, the picture information is read from the hard disk device 181. The display device 9 is connected to the graphics controller 6 and displays an output of computer including the picture information on the computer screen.
FIG. 8 shows a block diagram for explaining a video decoder of a prior art. A composite signal 250 is inputted to an input terminal 220 for a video signal of a computer and is separated into brightness signal (Y) and color signal (C) through Y/C separator 301. Y/C signal 251 is separated into a picture signal and a synchronizing signal 253 through NTSC decoder 302.
Y/C signal 251 of the picture signal is separated into YUV 252 (brightness and color difference). YUV 252 is converted to a digital signal by analogue/digital (A/D) converter 303 and both the digital signal and the synchronizing signal 253 are inputted to matrix circuit 254.
FIG. 9 is a time chart for explaining a video signal (analogue) including a copy guard signal. As shown in FIG. 9, a video signal of a television screen includes a vertical synchronizing pulse 200, a horizontal synchronizing pulse 201, and an image signal 202. The copy guard signal 210 inserted between a vertical blanking interval, not displayed at the television screen has a higher level than the image signal 202 in voltage.
NTSC decoder 302 in FIG. 8 separates the synchronizing signal 253 of the video signal from Y/C signal 251. When A/D converter 303 digitizes YUV 252, the copy guard signal 210 is dropped.
FIG. 10 is a time chart for explaining the video signal (digital) after A/D conversion. The signal 270 in FIG. 10 shows that the copy guard signal 210 is dropped. When the analogue signal is converted to the digital signal, the highest voltage level of the image signal 202 is defined as a standard. Therefore, if there is no function for detecting a copy guard signal, the high level in voltage of the copy guard signal is missing when YUV 252 is digitized.
FIG. 11 shows a time chart of the synchronizing pulse (the vertical synchronizing pulse 200 and the horizontal synchronizing pulse 201) after NTSC decoder 302 separates from Y/C signal 251. The picture information is obtained from the synchronizing pulse (200, 201) and the image signal 202 (digital) shown in FIG. 10. The picture information is recorded and reproduced on the computer system.
When an output terminal for a video signal such as the output terminal 202 is provided to a computer, it is possible to output video signal of pictures on the computer screen. And a copy guard signal might be dropped, even though the video signal including the copy guard signal is inputted. Thus, there is a problem such as it would be likely to reproduce pictures or audio programs in spite of having a copy guard signal, if VTR for recording is connected to the output terminal for a video signal of a computer.